Raspberry Pi Magnetometer
Real-time observations from Louisville, CO
Live Data
I monitor Earth's magnetic field from my backyard in Louisville, Colorado using an RM3100 magnetometer on a Raspberry Pi. Data from the USGS Boulder Observatory (~10 miles north) is plotted alongside for comparison.
Two dashboards are available: magnetic coordinates (H, E, Z, F) as measured by the sensor, and geographic coordinates (X, Y, Z, F) rotated by the local magnetic declination (~7.8°).
About This Station
The station measures four components of the geomagnetic field in the HEZ coordinate system: horizontal intensity (H) pointing toward magnetic north, magnetic east (E), vertical intensity (Z) pointing downward, and total field (F). Variations in these measurements indicate geomagnetic storms and substorms caused by solar activity.
Installation
The magnetometer uses a PNI RM3100 magneto-inductive sensor with a noise floor of ~4 pT/√Hz at 1 Hz. I ordered the kit from HamSCI and followed their PSWS Ground Magnetometer installation guide.
The sensor is housed in a PVC pipe and buried vertically approximately 3 feet underground for temperature stability and electromagnetic isolation. It is oriented so the H-axis points toward magnetic north, determined by rotating the assembly until the E component reads near-zero. A shielded CAT6 Ethernet cable runs underground to my shed, where the Raspberry Pi handles data acquisition and transmission to a cloud database.
Since the sensor is in a residential backyard exposed to various sources of magnetic noise, I expect a resolution of 10–20 nT. The raw 1-second data exhibits a periodic fluctuation with a period of ~10–11 seconds and amplitude of approximately 10 nT, which is not removed before averaging to 1-minute data.
Baseline Corrections
To compare the Raspberry Pi readings with USGS Boulder Observatory data, bias corrections are applied. These offsets account for differences in sensor calibration, local crustal anomalies, and the ~10-mile distance between the two sites.
Bias values were determined from the median difference over approximately 60 days of observations (November 2025 – January 2026):
- H +490.7 nT
- Z +3914.4 nT
- F +3767.7 nT
- X +486.2 nT (derived from H × cos 7.8°)
- Y +66.6 nT (derived from H × sin 7.8°)
Installation Photos
